So because it doesn't (according to you) "interact" with our natural world in a way that you can't distinguish means we can (according to you) "never" know about it?
It can't really be determined by anybody. You may think it interacted with you, but there is as of yet no way of telling if it actully did. It is indistnguishable from a delusion, or aliens with thought ray devices. That is what Tangle meant. Iḿ not saying your delusional, by the way, I'm trying to explain the reasoning here.
What do you mean by "it doesn't matter to us if it does"?
He means that if it doesn't interact with the natural world in a way we can clearly distinguish, then it doesn't matter if it exists because it will never interact with us. And things that don't interact with us are irrelevant, by all intents and purposes.